LEAD ISOTOPIC EVIDENCE FOR A MIXED PROVENANCE FOR ROMAN WATER PIPES FROM POMPEII*

Lead isotope analysis has been applied to the investigation of some Roman objects found in the town of Pompeii, consisting mostly of fistulae from the Augustan water supply system. The results of the analyses have produced ratios between 18.10 and 18.66 for ²⁰⁶Pb/²⁰⁴Pb, between 15.63 and 15.72 for ²⁰⁷Pb/²⁰⁴Pb and between 38.21 and 38.98 for ²⁰⁸Pb/²⁰⁴Pb. These data point to a fairly complex origin for the lead artefacts, probably involving several successive meltings and recyclings of a rather heterogeneous lead supply. The spread of lead isotope ratios can only be reconciled with a multiplicity of end‐members, at least three, but very probably more. There is one certain Sardinian ore, other indistinguishable Hercynian ores of Sardinia and/or Spain, and several different Alpine Mesozoic‐Tertiary mineralizations of the Mediterranean basin (Spain, Greece, Tuscany).     

MULTI‐METHOD MARBLE PROVENANCE DETERMINATIONS: THE CARRARA MARBLES AS A CASE STUDY FOR THE COMBINED USE OF ISOTOPIC,ELECTRON SPIN RESONANCE AND PETROGRAPHIC DATA*

A multi‐method approach, based on petrography, stable isotope data and electron spin resonance spectroscopy for assigning the provenance of white marbles, is presented. A total of 11 experimental variables has been used, including the quantitative measurement of the sample colour and its homogeneity. On this basis we attempt to distinguish the three main quarrying basins of the Carrara district, that is, Torano, Miseglia and Colonnata. Such discrimination, extremely uncertain on the basis of the single techniques, may be performed with acceptable confidence’ using a properly selected subset of six petrographic, isotopic and spectroscopic variables. The final resubstitution and jackknifed re‐assignment rates are, respectively, 85% and 81%. Inclusion of the remaining five variables into the classification rule does not improve the results, but simply increases data overinterpretation. The practical possibility of using such an approach for more general provenancing problems is considered.     

AN EXPERIMENTAL INVESTIGATION ON LEAD ISOTOPIC FRACTIONATION DURING METALLURGICAL PROCESSES

In this paper, experiments are designed to imitate the non‐equilibrium evaporation metallurgical process of lead. The lead isotope ratios of the remaining lead liquid with different percentage losses were then determined using high‐solution MC–ICP–MS. The results show that this process does alter lead isotopic ratios of the remaining liquid. However, the variations are so much smaller than the speculated values using the theoretical formula that in most ancient metallurgical processes, the lead isotopic fractionation can be neglected.     

MEDIEVAL LEAD GLASS IN CENTRAL EUROPE

In Trommsdorfstraße, Erfurt, a glass‐processing workshop has been excavated, which produced lead glass rings and beads in the 13th century. This workshop produced two different lead glasses. The first, a high‐lead glass, could be found throughout Europe, from England to Russia. However, another newly defined type of glass could be identified (Central European lead–ash glass). This can be demonstrated by analysing the literature, and it has been found in eastern Germany, Poland, Slovakia and the Czech Republic. A Slavic lead–ash glass with the same ash content as the Central European lead–ash glass but lower amounts of lead was produced in Eastern Europe. In western Germany, another type of ash (beech ash) was used to produce a wood‐ash lead glass. Lead‐isotope analysis proved that the same source of lead was used for the wood‐ash lead glass and the high‐lead glass in western Germany and the two types of glass from Erfurt.     

REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ¹⁸O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ¹⁸O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ¹⁸O_shell appears to be strongly influenced by seasonal inputs of very low δ¹⁸O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.     

‘THERE'S NO PLACE LIKE HOME’—NO ISOTOPIC EVIDENCE FOR MOBILITY AT THE EARLY BRONZE AGE CEMETERY OF SINGEN,GERMANY

The Early Bronze Age necropolis of Singen (Hohentwiel), located near Lake Constance, represents a population from a period of technological transition in southwestern Germany. The site contains several graves with metal artefacts that originated in other parts of Central and Western Europe, and therefore these could be interpreted as being the graves of non‐local individuals. The purpose of this study was to investigate this possibility through the application of isotopic analysis. The ratios of strontium and oxygen isotopes in human enamel reflect the geological origin of food and drinking water consumed during enamel formation in early life stages. Additionally, the ratio of sulphur isotopes from bone collagen reflects the origin of foods consumed during the last 10–20 years of life of an adult individual. We used these three isotope systems to attempt to identify local and non‐local individuals at the site. We found that the isotope ratios of Sr, O and S of the humans were relatively homogeneous and generally correspond to the isotope signature of the local geology, climate and environment. We conclude that the sampled population is of local origin and does not show patterns of individual mobility, even though there is evidence for long‐distance trade and exchange of the metal artefacts at this site.     

The Use of Strontium Isotope Analysis to Investigate Tiwanaku Migration and Mortuary Ritual in Bolivia and Peru

Strontium isotope analysis is applied in South America for the first time in order to investigate residential mobility and mortuary ritual from ad 500 to 1000. While Tiwanaku‐style artefacts are spread throughout Bolivia, southern Peru and northern Chile during this time, the nature of Tiwanaku influence in the region is much debated. Human skeletal remains from the site of Tiwanaku and the proposed Tiwanaku colony of Chen Chen have been analysed to test the hypothesis that Tiwanaku colonies, populated with inhabitants from Tiwanaku, existed in Peru. Strontium isotope analysis supports this hypothesis by demonstrating that non‐local individuals are present at both sites.     

The Characterization of Biologically Available Strontium Isotope Ratios for the Study of Prehistoric Migration

Strontium isotope analysis of bone and tooth enamel from prehistoric human skeletons is an important new technique used to address questions regarding migration. Two problems arise in such investigations: (1) levels of strontium isotope ratios in local bedrock, soil, water, plants and animals are variable; and (2) a range of values in human bone and enamel data make it difficult to distinguish some migrants from locals. Analysis of the bones of small animals provides a robust measure of local strontium isotope ratios and a reliable, if conservative, means for determining confidence limits for distinguishing migrants. Data from various geographical areas are presented here in a discussion of variability in strontium isotope values. Examples are provided using modern and prehistoric materials. We conclude with the recommendation that studies involving strontium isotope analysis should incorporate small animal samples for comparative purposes whenever possible.     

ROMANO‐EGYPTIAN RED LEAD PIGMENT: A SUBSIDIARY COMMODITY OF SPANISH SILVER MINING AND REFINEMENT*

Samples of red pigment from a group of seven Roman‐period Egyptian mummies, known as red‐shroud mummies, are investigated. Elemental analysis by inductively coupled plasma time‐of‐flight mass spectrometry (ICP–TOFMS) shows that the samples contain mostly Pb (83–92% by weight), along with 0.2–2.0% Sn. All of the samples are found to have similar trace element distributions when normalized to the continental crust, suggesting that they share a common geological origin. Lead isotope ratios are found to match the mixed lead sources typically associated with Rio Tinto, Spain – a site extensively mined for silver during the first century ad . Raman microspectroscopy identifies the major phase of each sample to be red lead (Pb₃O₄) with a minor phase of lead tin oxide (Pb₂SnO₄). Lead tin oxide does not occur naturally, and its incidental occurrence within the sample indicates that the material was heated under oxidative conditions at temperatures in excess of 650°C. In archaeological contexts, the high‐temperature oxidative treatment of lead is typically associated with metallurgical refinement processes such as cupellation. Based on this evidence, it is argued that the pigment was produced out of litharge associated with silver cupellation at the Rio Tinto site.     

MATHEMATICS,STATISTICS AND ARCHAEOMETRY: THE PAST 50 YEARS OR SO*

This review of developments in the use of mathematics and statistics in archaeometry over the past 50 years is partial, personal and ‘broad‐brush’. The view is expressed that it is in the past 30 years or so that the major developments have taken place. The view is also expressed that, with the exception of methods for analysing radiocarbon dates and increased computational power, mathematical and statistical methods that are currently used, and found to be useful in widespread areas of application such as provenance studies, don't differ fundamentally from what was being done 30 years ago.